The present invention concerns a combustion engine push rod element comprising an intermediate member, a push rod seat one end of which is intended to act on a rocker arm positioned adjacent a cylinder valve and the opposite end of which is intended to be attached to one end of the intermediate member, and a push rod end element one end of which is intended to abut against a valve lifter positioned adjacent the camshaft and the opposite end of which is intended to be connected to the opposite end of the intermediate member. The invention also concerns a method of manufacturing a push rod of this kind.
In combustions engines wherein the camshaft is in a low position, the transfer of motion from the cams of the camshaft to the various valve mechanisms of the cylinders is affected by means of push rods. In order to meet the demands both for low weight and high buckling strength tubular steel materials have been used for push rods of this kind in accordance with prior art technology.
Conventionally, the end of the push rod abutting against a valve lifter positioned adjacent the camshaft has a spherical configuration whereas the opposite push rod end which affects a rocker arm positioned adjacent the cylinder valve generally is cup-shaped.
In accordance with prior art technology both end pieces are separate components which are attached to the tube e.g. by welding. In this case welding is however a both costly and time-consuming method, in addition to which special equipment is required for its performance. As an alternative to welding the end pieces may be pressed on to the tube, a method which however requires that the various components are manufactured to strict tolerances. In addition, the tube must be machined internally.
The present invention has for its purpose to provide a push rod and a method of manufacturing a push rod, wherein the disadvantages outlined above have been removed. In addition, the invention concerns a simple method of assembling the push rod which may be performed at low costs and without requiring any or very few specialty tools. Furthermore, in mounting the end pieces onto the push rod tube it is also desirable that the forces acting on the tubular parts are reduced, allowing said parts to be manufactured with thin walls without risk that the walls will burst during assembly.